Long Lumbrical Muscle Exam

  • Origin: FDP tendon in Section 8 at level of the superficial arch.
  • Insertion: Radial lateral band (conjoined extensor tendon) at neck of proximal phalanx.
  • Innervation: Median nerve C6-T1, ulnar nerve C8-T1.
  • Nerve: Lumbricals II and III from median nerve lumbricals IV and V from the ulnar nerve.
  • The lumbricals flex the MP joints and extend the IP joints of the fingers.
Diagrams & Photos
  • Note lumbrical plus deformity during active flexion. The tendon graft was too long.
    Note lumbrical plus deformity during active flexion. The tendon graft was too long.
  • Note scar (yellow arrows) from previous tendon grafting.
    Note scar (yellow arrows) from previous tendon grafting.
  • Lumbricals are shown on the radial side of the flexors (FDP & FDS) of the index, long, and ring flexor sheaths.
    Lumbricals are shown on the radial side of the flexors (FDP & FDS) of the index, long, and ring flexor sheaths.
Key Points
  • The lumbrical plus finger occurs when the FDP is cut distally or lengthened by an overly long tendon graft. The result is proximal displacement of the lumbrical origin on the FDP tendon and exaggerated IP joint extension during finger flexion.
Grading of Muscle Strength
Exam References
Anatomic Abbreviations
Hand Surgery Resource Exams & Signs Library